Impact Craters May Be the Wrong Places to Look for Life on Mars

Have we been looking for signs of Martian life in the wrong place? A new study claims that meteorites may destroy all signs of life that may have existed within their impact craters, which is one of the most popular places for scientists to search for life.

Mars is covered with small and large craters from meteorite impacts, and they have been a key target for astrobiologists searching for alien life. The theory behind this strategy is that meteorite impacts may have blasted rocks from deep underground to the surface, and any organic compounds that are signs of past or present life could likely be found beneath the surface, away from the harmful solar radiation that would degrade the compounds.

Now, a team of scientists from Imperial College London has tested that theory—and it doesn't hold up. In order to determine whether organic compounds encased in rock could survive being blasted to the surface by a meteorite, the researchers simulated ten blast impacts in the lab for meteorites approximately ten meters in diameter. In their study, published in Scientific Reports, they found that the intense pressure of the impact had actually wiped out all signs of the organic compounds associated with microbial and algal life. As a result, they concluded that the impacts would have wiped out all signs of life, even if it had, in fact, existed beforehand.

"The study is helping us to see that when organic matter is observed on Mars, no matter where, it must be considered whether the sample could have been affected by the pressures associated with blast impacts," team member Wren Montgomery said in a statement. "We still need to do more work to understand what factors may play an important role in protecting organic compounds from these blast impacts."

Although the fact that meteorites have destroyed signs of life sounds discouraging on its face, it's actually a boon for the search for alien life on Mars. If we've been looking in the wrong places this entire time, then this discovery may point us to the right places to look in the future. The researchers believe that their study could help future Mars missions zero in on the locations that would be most likely to harbor Martian microbes or other forms of life.

"We've literally only scratched the surface of Mars in our search for life, but so far the results have been inconclusive. Rocks excavated through meteorite impacts provide scientists with another unique opportunity to explore for signs of life, without having to resort to complicated drilling missions. Our study is showing us is that we may need to be nuanced in our approach to the rocks we choose to analyse."